1. Field of Endeavor
The present invention relates to and more particularly to a composite of polymers and carbon nanotubes, and more particularly, to a mechanically stiff, electrically conductive composites of polymers and carbon nanotubes.
2. State of Technology
The treatise, Introduction to Nanotechnology, by Charles P. Poole, Jr., and Frank J. Owens, John Wiley &. Sons, 2003, states: “Nanotechnology is based on the recognition that particles less than the size of 100 nanometers (a nanometer is a billionth of a meter) impart to nanostructures built from them new properties and behavior. This happens because particles which are smaller than the characteristic lengths associated with particular phenomena often display new chemistry and physics, leading to new behavior which depends on the size. So, for example, the electronic structure, conductivity, reactivity, melting temperature, and mechanical properties have all been observed to change when particles become smaller than a critical size.”
Carbon nanotubes (CNTs) possess a number of intrinsic properties that make them promising candidates as filler material in the design of new composite systems. CNTs can have electrical conductivities as high as 1×106 S m−1, thermal conductivities as high as 3000 W m−1 K−1, elastic moduli of the order of 1 TPa, and are extremely flexible. Unfortunately, the realization of these properties in macroscopic forms, such as conductive polymer/CNT composites, has been limited. In these composites, CNTs are typically dispersed throughout the polymeric matrix by addition of the individual nanotubes or bundles to precursor formulations. Since the loading levels and distribution of the CNTs in the polymer determine the conductivity of the composite, one of the challenges associated with the fabrication of conductive polymer composites is attaining uniform dispersion of the CNTs within the matrix. In addition, dispersion methods can vary greatly depending on the characteristics of matrix material. While measurable increases in electrical conductivity can be achieved through addition of as little as 0.007 wt % CNTs to polymer matrices, preparation of composites with conductivities >1 S cm−1 requires either higher loadings of CNTs (>10 wt %) or specially-designed CNTs that facilitate dispersion in the matrix. Thus, the fabrication of CNT-polymer composites with conductivities on par with highly conductive semiconductors and metals for applications such as electromagnetic interference shielding can be an expensive endeavor. An attractive alternative to the dispersion approach for the design of conductive polymer composites would be the use of a low-density, electrically conductive CNT foam as a scaffold that can be filled or infiltrated with the polymer matrix. With this approach, the uniformity of the dispersed phase, and hence the conductivity of the composite, is established by the pre-formed CNT network of the scaffold. In addition, this approach could be general and utilized with a wide variety of polymer matrices.